The present invention relates to optical data disks such as compact disks (CDs) and video disks (DVDs) that have central circular locating openings, and more particularly to devices for protectively enclosing such disks for storage of same.
Data disks such as compact disks and video disks typically have large amounts of digitally stored information that is optically readable through a transparent bottom layer of the disk by a movable head during rotation of the disk. The information is arranged in one or more tracks that are covered by a thin protective top layer of the disk that can have labeling applied thereto such as by silkscreening. Normal handling of the disk can result in scratching of the bottom layer, resulting in loss of data by interference with the optical path such as by loss of focus and/or lateral image displacement. Also, data can be lost by scratching of the protective layer which is typically very thin, on the order of 20 microns, resulting in removal of information from a vapor deposited metal layer that is only about 0.1 micron thick. Protective containers for the disks in common use have a central pedestal for supportively gripping the disc by engaging the central opening without contacting either side of the disk within data-containing regions thereof. Such containers typically have a ledge for contacting portions of an outer perimeter of the disk for stabilizing the disk against tipping on the pedestal. The disk is loaded into the container by lowering it onto the pedestal while gripping opposite perimeter portions, engagement with the pedestal being typically effected by simultaneous finger pressure against the disk proximate the central opening. Removal of the disk is similarly effected by finger pressure against the pedestal and simultaneous lifting at the perimeter portions. U.S. Pat. No. 5,685,427 to Kuitems et al. discloses a compact disk holder having a central post that projects from a shoulder surface, the post having an outwardly facing ridge for gripping the disk opposite the shoulder surface. The post is formed with spiral slots for contraction of segments in response to finger pressure. A disadvantage of the holder of Kuitems is that it is difficult to use in that excessive finger pressure is required for contracting the segments; conversely, if the segments are made sufficiently long and thin for contracting under reasonable finger pressure, they are too weak to be effective in holding the disk.
U.S. Pat. No. 5,526,926 to Deja discloses a disk storage case having a segmented central pin that is formed with an outwardly projecting collar for gripping the central hole of the disk, the pin being connected to an outwardly projecting plurality of lifting fingers that pivot upwardly when the pin is contracted by pressure on a central push-button. A disadvantage of the case of Deja is that the fingers are ineffective in that they must be sufficiently elastic to permit depression of the push-button prior to actual lifting of the disk, and they do not retain sufficient elastic strength for reliably lifting the disk, in that projection portions of the fingers have limited length. UK Patent Application No. 2,291,640 (and U.S. Pat. No. 5,788,068) by Fraser et al. discloses a compact disk holder having a bifurcated button supported on respective inwardly projecting spring arms, segments of the button being interconnected by a living hinge in some embodiments. Also, some embodiments have a plurality of inwardly projecting disk ejection spring arms spaced about the button for lifting the disk when the button is depressed. Other embodiments rely on an outer ledge for support of the disk, which flexes when the button is depressed, the center portion of the disk being lifted by resilience of the disk when the button is sufficiently depressed to effect disengagement. The holder of Fraser et al. has a number of disadvantages. For example:
1. The ejection spring arms are prone to be damaged by being snagged by objects such as a user's clothing;
2. The disk is subject to damage by rubbing of the ejection spring arms; and
3. The flexing of the disk is ineffective in reliably completing disengagement from the button in the absence of the ejection spring arms.
Thus there is a need for a protective disk container that overcomes the disadvantages of the prior art.